Heroic Summon - Missing

I just used 300 gems to summon a hero and was thrilled to see that it unlocked Yokozuna. I then used a bunch of xp potions to bring him up to level 21, then the game glitched. When it reloaded, Yokozuna was gone, my gems and potions were not returned. What happened? How do I either get my summon back, or a refund on the stuff I used to summon and level him up?